Diabetic Retinopathy

By Kenneth N. Darvin, M.D.

Anyone can get diabetes; some people are at higher risk. These include people who have relatives with diabetes, people who are overweight, African Americans, Hispanics, Native Americans, the elderly, Asian Americans and those who had gestational diabetes. It is estimated that five million people in the U.S. have diabetes and do not know it. Symptoms develop gradually, or in some cases there are no symptoms at all. Some symptoms are: increased thirst, frequent urination, unexplained weight loss, increased hunger, blurry vision, recurring skin infections, wounds that do not heal, and unexplained fatigue.

There are two main types of diabetes: type I and type II. Type I diabetics have lost the ability to produce insulin, the hormone that regulates glucose in the blood. Type II diabetes most often occurs in adults, accounts for 90% of cases in the U.S. and is often associated with obesity and with fat in the abdominal area. These diabetics have insulin, but their body is resistant to it. With these patients exercise and weight loss is important in the treatment regimen, along with oral medication. With type I diabetes, treatment consists of administration of insulin and dietary changes.

Diabetic retinopathy is the leading cause of blindness in patients under 65. Diabetic retinopathy is broken down into two types: proliferative and non-proliferative.

Non-proliferative, background diabetic retinopathy, is usually the early stage where blood vessels dilate and can leak blood, fluid, or both. Sometimes the leakage is greater than the body's ability to resorb it, and the retina becomes swollen. If the swelling occurs within the central part of the retina, the macula, where fine central vision is located, laser treatment is undertaken. The purpose of the laser is to shut down the leaking blood vessels and have the retina resorb the fluid, hoping to maintain vision and prevent further visual loss. This type of complication from diabetic retinopathy can be reduced by 50% with laser treatment.

In proliferative diabetic retinopathy new blood vessels begin growing on the surface of the retina and/or the optic nerve. The main cause is widespread closing of blood vessels leading to ischemia, causing chemical factors to be released in the back of the eye and new blood vessel growth. Current mainstay treatment is pan-retinal photocoagulation, where the peripheral retina is lasered to cause these blood vessels to regress. Once again, appropriate laser treatment can prevent severe visual loss by 50%. The visual loss is secondary to new blood vessels that scar, shrink and wrinkle the retina, and can even cause a detachment of the retina.

Proliferative diabetic retinopathy can also lead to a vitreous hemorrhage, when new blood vessels bleed into the vitreous cavity, causing a decrease in vision or a tractional retinal detachment. A vitreous hemorrhage or tractional retinal detachment can be operated on by a procedure called a vitrectomy. Final vision will depend upon the health of the underlying retina.

At times, neovascular glaucoma can occur. this happens when new blood vessels grow that are normally not found in the eye and are found on the iris, the colored part of the eye, and even into the angle, which is a drain for the fluid within the eye. These blood vessels grow and block the angle, causing a very high intraocular pressure which is very hard to relieve without surgical intervention.

It is very important that diabetics have their eyes screened or examined with a dilated retinal exam once a year. If any retinopathy is found, that interval would be decreased depending upon severity.